Question

find the least number n so that 5n is divisible by 3,where n is a natural number​

Answer 1

Answer:

3

Step-by-step explanation:

let n=3,

hence,5n=5×3=15,

hence 15 is divisible by 3.

Answer 2

Given: 5n where n is a natural number is divisible by 3

To find: Least value of n

Solution: A number is divisible by 3 when the sum of its digit is divisible by 3.

For example-

33-> The sum of its digit is (3+3)=6 which is divisible by 3, therefore the number 33 is also divisible by 3.

76-> The sum of its digit is (7+6)=13 which is not divisible by 3, therefore the number 76 is also not divisible by 3.

Here, for the number 5n to be divisible by 3, the sum of digits (5+n) should be divisible by 3.

By hit and trial method, we notice that in place of n when 1,4 or 7 is kept,the sum of digits become 6,9 and 12 respectively which are divisible by 3 and hence the number also becomes divisible by 3.

The least number among 1,4 and 7 is 1. The number when 1 is placed in place of n is 51 which is clearly divisible by 3.

Therefore, the least natural number n is 1.